Stefan J. Long

Sirex species (Hymenoptera: Siricidae) and their parasitoids in Pinus sylvestris in eastern North America.

Abstract Siricids and their parasitoids were reared from Scots pine (Pinus sylvestris L. (Pinaceae)) trees infested by Sirex noctilio F. in central New York State. Sirex noctilio accounted for 94.3% of the siricid specimens emerging, totaling 1313 specimens from six trees, with a maximum of 495 from one tree. Of the individuals emerging per tree, 20.6 ± 5.2% were female. Two native siricids, Sirex nigricornis F. and S. edwardsii Brullé, also emerged from trees but in low numbers. Three hymenopteran parasitoid species that attack siricids emerged, totaling 21.8 ± 6.4% parasitism per tree. Ibalia leucospoides ensiger Norton (Ibaliidae) was by far the most abundant parasitoid, at 20.5 ± 6.3% parasitism per tree. The percentage of female S. noctilio emerging was positively correlated with wood diameter, whereas percent parasitism by I. l. ensiger was negatively correlated with wood diameter.

Impact of Exposure Length and Pupal Source on Muscidifurax raptorellus and Nasonia vitripennis (Hymenoptera: Pteromalidae) Parasitism in a New York Poultry Facility

Abstract Commercially obtained Nasonia vitripennis Walker and Muscidifurax raptorellus Kogan & Legner were released weekly for 12 wk into a high-rise, caged-layer poultry house. After the release period, parasitoids were sampled using sentinel house fly (Musca domestica L.) pupae that were either laboratory-reared or field-collected as larvae and exposed for 2, 4, 7, and 14 d. Parasitoid-induced mortality was observed in 31% of laboratory colony pupae and in 26% of field-collected pupae, whereas successful parasitism rates of 48 and 51% were observed from these pupal sources, respectively. Parasitism was primarily by M. raptorellus (88%), and Muscidifurax raptor Girault & Sanders (11%), while N. vitripennis accounted for <1%. Percent female progeny ranged from 43% in M. raptorellus to 76% in N. vitripennis. Parasitoid emergence from 2-d exposed sentinel pupae was the lowest of all treatments. Parasitoid emergence from 7-d exposed sentinel pupae was the highest of all treatments. We found no differences between pupal source, suggesting that when sampling for M. raptor, M. raptorellus, and N. vitripennis, in poultry facilities, pupal source is not a confounding factor.

Parasitism Rates of Muscidifurax raptorellus and Nasonia vitripennis (Hymenoptera: Pteromalidae) After Individual and Paired Releases in New York Poultry Facilities

Abstract Commercially reared parasitoids were released into three high-rise, caged-layer poultry houses; one house received only N. vitripennis Walker, the second house received only M. raptorellus Kogan & Legner, and the third house received an equal ratio of both species. Overall, house fly parasitism by M. raptorellus was never higher than 7% in any house. Most parasitism in the M. raptorellus release house was attributed to N. vitripennis. Parasitism of house fly pupae by M. raptorellus did not significantly increase during or after the 6-wk release period in the house that received both parasitoids. However, a depression in total parasitism was not detected when releases of the two species were made in this house.

Phylogenetic analysis of Deladenus nematodes parasitizing northeastern North American Sirex species.

The parasitic nematode Deladenus siricidicola is a biological control agent of the invasive woodwasp, Sirex noctilio. Since the discovery of S. noctilio in pine forests of northeastern North America in 2005, a biological control program involving the Kamona strain of D. siricidicola has been under consideration. However, North American pine forests have indigenous Sirex spp. and likely harbor a unique assemblage of associated nematodes. We assessed phylogenetic relationships among native Deladenus spp. in the northeastern United States and the Kamona strain of D. siricidicola. We sequenced three genes (mtCO1, LSU, and ITS) from nematodes extracted from parasitized Sirex spp. collected inside and outside of the range of S. noctilio. Our analyses suggest cospeciation between four North American Sirex spp. and their associated nematode parasites. Within two S. noctilio individuals we found nematodes that we hypothesize are normally associated with Sirex nigricornis. One individual of the native S. nigricornis contained Deladenus normally associated with S. noctilio. We discuss nematode-host fidelity in this system and the potential for non-target impacts of a biological control program using D. siricidicola against S. noctilio.

Variability in growth of Deladenus siricidicola on strains of the white rot fungus Amylostereum areolatum

Deladenus siricidicola nematodes are used extensively for biological control of Sirex noctilio in the southern hemisphere. They have one morph that is parasitic on S. noctilio and another that feeds on the white rot fungus Amylostereum areolatum and is used for mass production of the nematode. To examine potential effects of strains of A. areolatum found in North America on D. siricidicola in a biological control program, first we compared the growth of four isolates of A. areolatum on several types of artificial media. We then evaluated the ability of D. siricidicola to survive and increase on five isolates of A. areolatum and found that nematode populations persisted on all five isolates. One of the slowest growing fungal isolates, ScyME, produced the most nematodes when the fungus was given five and ten days of growth prior to nematode inoculation, while the fastest growing fungus, Aussie, never produced the most nematodes. Although nematodes in all treatments produced eggs, D. siricidicola populations were unable to replace themselves when feeding on the fungal isolate SedDF. The differential ability of D. siricidicola to persist on different isolates of A. areolatum found in North America could affect multiple aspects of a biological control program to control S. noctilio.

Prey- and Density-Mediated Dispersal in Carcinops pumilio (Coleoptera: Histeridae), a Predator of House Fly (Diptera: Muscidae) Eggs and Larvae

Abstract Carcinops pumilio (Erichson) were collected using two trapping methods: a black light pitfall trap and a mesh-bottomed trap placed on poultry manure. C. pumilio collected with black lights and subsequently starved had a significantly higher dispersal rate during days 1-3 than fully fed groups. When densities of <500 Caloglyphus berlesei (Michael) (Acarina: Acaridae) per 50 C. pumilio were provided, mite availability had a significant effect on dispersal of beetles captured with both black light traps and the mesh-bottomed trap during the day 1-3 period. Our results indicate that the availability of acceptable food sources can delay and possibly prevent dispersal by C. pumilio. Black light-captured beetles appeared to be in a state of dispersal when captured. A subset of dispersing beetles was present in groups captured with the mesh-bottomed trap.

Larval Production from Field-Collected Carcinops pumilio (Coleoptera: Histeridae) Following Three Starvation Periods

Abstract Carcinops pumilio (Erichson) were collected from high-rise, caged-layer poultry facilities using two trapping methods, a blacklight pitfall trap and a mesh-bottomed trap placed on poultry manure. Starvation for 14 d significantly reduced larval production during the first 3-d oviposition period regardless of trapping method. Beetles collected with blacklight traps and subsequently starved for 14 d had higher larval production in the third through fifth oviposition periods than those fed daily, indicating that lack of nutrition was a limiting factor in C. pumilio larval production. No differences were observed in larval production, after the first oviposition period, between the 14-d starved and daily fed groups collected with the mesh-bottom trap. In all blacklight-captured treatments, larval production was lowest during the first oviposition period with the largest differences found among the three starved treatments. Larval production in the 14-d starved treatment increased significantly during the later oviposition periods in mesh-bottom trap studies. Within the fed treatment, larval production was consistently greater among beetles collected with the mesh-bottom trap than among beetles collected with blacklight traps.

Host age and pathogen exposure level as factors in the susceptibility of the house fly, Musca domestica (Diptera: Muscidae) to Beauveria bassiana

Abstract Adult house flies, Musca domestica L., of four ages, <1, 3, 7, and 14 day post-eclosion, were exposed to three strains of Beauveria bassiana (P89, L90 and 447). Flies were exposed to moistened filter paper treated with either a low (1.57×104 conidia/cm2) or high (1.57×105 conidia/cm2) concentration of each fungal strain for 6 h. Strain 447 was superior to the two house fly-derived B. bassiana strains in inducing host infection and mortality. Significant spikes in infection and mortality occurred as early as 5 days post-exposure with higher concentration exposures acting more quickly. Few differences were observed in either infection or mortality among the four fly age classes. On Day 10 post-exposure, 77% of the high-concentration, 447-exposed flies were infected, compared with only 24% of the flies from the P89 low-concentration exposure. Potential applications of these results in integrated house fly management programs are discussed.

Symbionts mediate oviposition behaviour in invasive and native woodwasps

Globalization leads to the introduction of invasive species that are often accompanied by associated microorganisms, and this can lead to homogenization of both introduced hosts and microbes with the native biota. One such example is the invasive Eurasian woodwasp Sirex noctilio, which inoculates pines with an obligate nutritional mutualist, the white rot fungus Amylostereum areolatum. Although S. noctilio has been previously introduced outside of its native range, its arrival in North America was the first time that it was introduced to communities hosting native Sirex species and Amylostereum strains. We conducted experiments aiming to investigate acceptance versus avoidance of native and non‐native Amylostereum strains and species during ovipositor drilling by females of S. noctilio and a native congener, Sirex nigricornis. Sirex noctilio preferred wood without prior fungal emplacement, whereas S. nigricornis preferred wood inoculated with one of the strains of Amylostereum that putatively invaded with S. noctilio. Drilling and presumed oviposition by both woodwasp species were highly aggregated. Based on the responses of these two Sirex species to the fungal strains and species included in the present study, the invasive S. noctilio would continue its present symbiont associations, whereas the native S. nigricornis would partly use the strain of fungal symbiont putatively introduced with S. noctilio.